ill make it easier... it only works on shortcuts.. so presuming you have a d2x shortcut on your desktop, right click on it and click on properties... you want to go to the bit whihc says target and it should look something like this in the text box: "c:\games\diabloII\diabloII.exe" or what ever, then u want to add a -w to the end of that.. make sure there is a space between the " and the -w so it should look like "c:\games\diabloII\diabloII.exe" -w

btw one more thing is that if you insert the cd and you click play from the autorun menu, d2 wont run in a window as you need to use the shortcut you edited...